


Hotter than Hell

by knowmeknot



Category: Undertale (Video Game)
Genre: Bone Fondling, Double Penetration, Dubious Consent, Light Bondage, Multi, Multiple Orgasms, Overstimulation, Possessive Behavior, Rough Sex, Sensation Play, Sensory Deprivation, Sexual Coercion, Sexual Exhaustion, Soul Sex, Souls as genitalia, Voyeurism
Language: English
Status: Completed
Published: 2017-06-09
Updated: 2017-06-09
Packaged: 2018-11-11 14:25:24
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,208
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11150280
Author URL: https://archiveofourown.org/users/knowmeknot/pseuds/knowmeknot
Summary: Grillby ignored Sans's more than obvious flirting, believing it was nothing more than a prank. Until he sees this purple asshole of himself getting more intimate with his skeleton than he liked.





	Hotter than Hell

**Author's Note:**

  * For [Askellie (NadaNine)](https://archiveofourown.org/users/NadaNine/gifts).



> This is for Askellie based off [this post](https://askellie.tumblr.com/post/160787807159/special-service) and the accompanied fanart by arice-art. I tried to incorporate all the ideas you gave me. Hopefully it didn't turn out too bad. 
> 
> This was also written to quench my Sansby thirst.

Grillby flickered as he watched Sans shuffle out of his bar, shoulders slumped. He locked the front door, grabbed a clean rag and began to scrub the place down. His thoughts wandered back to the small skeleton. For the past several weeks, Sans had been staying at his bar so late, sometimes even past closing, that Grillby had to kick him out, like tonight for instance. Sans’s jokes have also become more and more… suggestive.

_“hey grillbz, what’s the weather like when you show up? hot and sunny,” Sans had made a gesture to fan himself, accompanied with a wink._

_“i see steam every time i look at you.”_

_"i like my monsters how i like my peppers, orange and sizzling.”_

Had Sans been flirting with him? That couldn't be.

It wasn't as if Grillby disliked Sans; in fact, he enjoyed the other’s company - after all, Sans had always supported him since they’d first met - and could even say he loved the skeleton comedian. However, he simply couldn't figure out why Sans would find an old fire elemental like him attractive, especially since he was nearly a decade older than Sans. And Grillby wouldn't put it past Sans that his flirtatious attitude was all an elaborate prank. Every time Grillby asked if Sans was being serious, he would brush it off as a joke, and begin punning at Drunk Bun.

Grillby had just thrown out the trash in the back of his establishment - it was covered with black coals instead of snow - when the ground rumbled. Grillby peered around, wondering where it had come from. In a split second, a stifling darkness enveloped his surroundings, and he felt a sharp pull at his entire being.

When the world came back into view, Grillby found himself standing in the center of his empty bar, with Punk Hamster and a purple-colored elemental standing near the entrance. A vicious, wide grin adorned the flames making up his head, and the place of his eyes were a shade darker. This other fire monster wore no glasses.

“I am Chillby, the owner of his establishment,” the monster introduced with a sweep of his arms. His voice sounded similar to Grillby’s own. “Who are you?”

“...Grillby…”

“Oh, another me, eh? Is this another one of Sans’s pranks?” 

Grillby started at the mention of his friend’s name.

Chillby took a few steps towards him. “Let’s see who’s the better one.”

A loud popping sound came from Chillby, as the elemental sprang up, aiming a fiery punch at him. Grillby jumped back to evade the attack and bumped into a wooden door. His flames increased in temperature and expanded to twice their normal size, enough to burn through the door. He stumbled into the kitchen. Just like his own bar, the back exit stood in the opposite wall.

“If you’re hoping to escape, I’ll be more than happy to assist you.” 

Purple embers surrounded him without warning, and the force of the other’s kick sent Grillby flying across the room. A dark, furry rodent sped across the room and pulled the door open, just in time for Grillby to crash through it and land outside.

Outside where, instead of the ground lined with coals, it was filled with piles of snow. 

Grillby crashed headlong into one of the larger piles. His vision spun and dizziness crashed into him as the white substance seeped into his core. His HP and fire dwindled down to such dangerously low levels that even a glass of water would have been enough to end him. Rough, furry hands seize his arms and force them behind his back. Thick ropes were wound tightly around his arms, securing them in place. Punk Hamster, for how small he was, forced him into a kneeling position, keeping his head held close to another snow pile.

“Now what to do with you?” Chillby sneered, stalking towards him.

Out of no where, a series of white bones shot towards the purple flame monster, who jumped back to evade the attack. Grillby was jerked back. Blurrily, he looked around as much as he could and spotted Sans standing behind him. Several giant skeletal animal skulls surrounded Chillby. Quicker than the blink of an eye, Grillby’s flame was forced downward, mere inches from the snowpuff.

“As soon as you attack me, you can say good-bye to this other me.”

Sans Checked him. Grillby’s soul dropped at the sight of the skeleton’s stricken and guilty expression. He needed to get free and stop Sans from doing something foolish. But try as he might, Grillby couldn't burn through the ropes binding him. He didn’t have enough magic to burn through them. It didn't help that Punk Hamster pressed his heated body so close to the snow.

“If you do as I say, I will not harm your friend.”

Sans remained silent, though the goat skulls disappeared. 

The split in Chillby’s flame widened. He pointed at Punk Hamster and ordered, “You are to keep him near the door but outside. Do not let go of him.”

Grumbling, Punk Hamster dragged Grillby until they were in the doorway of the kitchen. Chillby and Sans entered back into the kitchen. Grillby struggled feebly against Punk Hamster’s hold, but it was to no avail. At least the hamster was kind enough to place Grillby’s glasses back on.

Chillby grabbed a wooden chair, set it down in the center of his kitchen and sat down. He loosened his black tie and unbuttoned his dress shirt to expose his fiery chest. Then he turned his attention to Sans, who stiffened.

“You are Sans?”

Said skeleton nodded. 

“You look quite different from the one I know.”

“like snowflakes, not all sanses are the same," Sans answered evenly with a shrug.

Chillby’s soft chuckle nearly froze Grillby’s soul.

“Alright. Strip.”

Sans remained still, staring at Chillby as if he'd been slapped in the face.

“What's wrong? I’ll keep my end of the bargain,” Chillby glanced at Grillby and the snow in warning. “It’s only fair that you keep yours as well.”

Grillby crackled in agitation. “Sans… don't.”

Sans gave him a tight grin. “sorry for gettin’ ya into this mess, bud.”

Slowly, and with his eye lights directed at the ground, Sans slipped off his trademark blue jacket, grasped the edge of his white shirt, and pulled it over his head, exposing his unmarred spine. Delicate white ribs gleamed in the dim light, and Grillby’s soul fluttered with sudden desire.

He wanted to wreath those smooth bones in his flames. To smother the small skeleton in them.

A tinge of blue dusted across Sans’s cheekbones as his face came back into view. Shaky, bony phalanges halted at the band of his shorts. Chillby brightened and expanded with excitement, which only renewed Grillby’s struggling. Tickles of coldness suddenly seeped onto him, the pain from it causing him to grunt. Sans glanced back at him with wide sockets, his white eye lights as pinpricks. 

“Continue,” Chillby commanded. “Or else.”

The threat had Sans pulling down his black track shorts without hesitation. With his last articles of clothing off, his socks and pink slippers, Sans was naked before them.

Grillby felt a pressure build within his soul at the sight.

Sans directed his pupils back at the wooden polished floor, not daring to glance at either fire monsters. He shifted his hands in front of his pelvis in a vain attempt to cover himself.

“Good. Now come here.” Chillby spread his clothed legs and beckoned Sans over with his right hand while his left tugged off the tie. 

Sans didn't move.

With a single warning glance at Grillby, Sans scrambled towards the native monster.

“Sans… No!” He couldn’t allow Sans to do this!

Grillby attempted to expand his form but being thrown into the snow had done more damage than he thought. 

Once Sans had reached Chillby, the violet-colored elemental ordered him to turn around. With his attention still locked onto the ground, Sans complied. He jolted when Chillby wrapped his tie around Sans’s skull, completely covering his eye sockets. Sans raised his arms to remove it, but Chillby seized both of Sans’s wrists.

“Ah ah, do not take it off.”

Chillby yanked Sans up into his lap, and forced the skeleton’s arms behind his back, keeping his carpals trapped together in Chillby’s left hand. Chillby used his right one to harshly fondle Sans’s lowest rib. Sans gasped sharply. 

Chillby shifted to a purplish-orange, though never reaching the same shade as Grillby’s own flames. The embers brushed across the outside and then flickered along the underside of Sans’s ribs. Sans arched into Chillby’s ministrations, panting raggedly, though he kept his teeth clenched in an attempt to remain silent. This only encouraged Chillby further, whose flames seeped between the vertebrae of Sans’s lower spine.

The pressure in Grillby’s core grew unbearable, and a burst of possessive rage overcame him. 

How dare Chillby touch _his_ Sans in this manner! 

Wait… was this… was he… Jealous of what his other self was doing to Sans?

As Chillby's invading touches continued, Sans’s soul gleamed brightly behind his ribcage. Grillby was horrified of what that suggested.

“My, my, Sans, you are really getting off on this, aren't you?” Chillby uttered softly by the skeleton’s skull, leering at Grillby. A fiery hand trailed down Sans’s spine, dipping between each vertebra and ripping violent tremors from the other. “Are you actually enjoying this?”

The skeleton in question could only gasp and pant loudly in response, cheeks darkening to indigo. 

The jealousy and fury in Grillby grew as he watched Chillby’s flaming head loom over the back of Sans’s neck. Chillby opened his jagged mouth and clamped down on the milky bone at the same time his blazing chest engulfed the skeleton’s spine.

Sans moaned loudly, causing the pressure in Grillby to manifest his magic as a flaming, hard cock. The crotch of Grillby’s pants grew bright orange, which did not go unnoticed by Chillby. The elemental’s smirk grew wide enough to nearly split his face.

“Or perhaps, because you are without your sight, you're imaging that Grillby is doing this to you? I increased the temperature of my flames for a reason.”

“ahh… grillbz… hah,” Sans groaned. A thin coating of cyan fluid covered his soul.

Grillby watched hungrily as the tips of Chillby’s fingers lightly brushed against the surface of the soul, coaxing it lower and lower until it hovered within Sans’s pelvis inlet. Chillby then stuck two fingers in between the humps of the inverted heart.

It should be _his_ fingers doing that to Sans’s soul.

Spurred by his heated desire, Grillby had an idea. 

“If you... have to blindfold Sans to pleasure him… then it's not even a competition… I can make him come faster and more times… than you ever could.” 

Chillby halted his teasing, causing a whine from Sans, and turned his attention completely to Grillby. Chillby deepened to a dark purple and the jagged mouth scowled deeply.

“You think you can? Hah! Don't make me laugh?”

“I bet… I can make Sans come in less time than you and more often... with the blindfold on… and without use of my hands!”

Chillby’s form expanded and darkened. “Oh? Bets are my specialty. But know that I only accept ones with high stakes, something worth dying for.”

“wait, grillbz,” Sans interrupted. Grillby caught, beneath the makeshift blindfold, the dark blue glow of the skeleton’s blush. “as _hot_ and all this is, heh, you don't gotta do this. it ain't worth putting your life in danger.”

Grillby found the statement hypocritical, given that Sans had been _coerced_ into this in exchange for his life. Not to mention, his life was already on the line. If things were going to end horribly, he would make sure at least Sans got out of this. Grillby’s burning desire would not let him back down.

“I bet… with my life.”

“Wait, wait, wait. Who said anything about betting your life? You are betting your freedom!”

“no, grillby, d—mmmph!”

Before Sans could finish, Chillby withdrew his right hand from Sans’s soul and shoved the magic-slick fingers into the small skeleton’s mouth, silencing any further protests. Sans huffed indignantly and tried to twist out of Chillby’s tight grasp, though it was a futile effort.

“As I was saying, will you bet your freedom in exchange for Sans’s?”

Grillby reeled for a second as he understood the implications of his counterpart’s words. 

Was he really that narcissistic of a monster? Or was he misunderstanding his other self?

Grillby leveled Chillby with a bemused look. Although Chillby’s arms and hands were an orangish purple, his head flashed between violet and indigo. Grillby had to admit that it was a nice shade, one that wasn't seen even among his fire brethrens in Hotland. This was not the Snowdin that he knew, despite some similarities.

Besides, this was for Sans. And he was not going to lose the monster that he had so obliviously ignored to another him.

Grillby stood as tall as he could and stated, “I will. And if I win… You will keep your flames off Sans and help us get home.”

Chillby’s embers bounced in the motion of a nod. “Fair enough, I'll accept your bet. Punk, back off.”

Said hamster, who had his left paw buried deep within his pants, let go of Grillby. With his arms still bound behind him, Grillby got up, swaying slightly as his vision swam, and stepped towards his counterpart.

“Your fire is weak. Let me help you some.” Chillby shifted forward in the chair, still keeping a firm grasp on Sans.

”Kneel to my level and summon your soul.”

Grillby faltered, and a muffled noise of protest escaped through the hand occupying Sans’s mouth.

“Don't worry, it’s only to restore some of your magic so you won't turn to ash. I am looking forward to this after all.”

Grillby would normally never even think of exposing his soul in a situation other than an encounter, but he wanted to do this for Sans. Besides, from what he could discern, this was some alternate of him, wasn’t it? Maybe he really was a closet narcissist.

“Don't worry Sans... I want to do this,” Grillby reassured preemptively. 

An inverted white heart hovered in front of Grillby’s chest. Chillby finally freed his right hand from Sans’s mouth to move towards the soul. The white organ pulsed brightly as Grillby saw the blue magic dripping from Chillby’s hand.

“grillby!” 

As soon as Chillby touched his soul, Grillby’s fiery form trembled violently. Instead of heat, his counterpart’s fire…

It was cold.

Although Grillby could control the temperature of his flames, he could never make it as cold as Chillby’s. He felt the cool embers wash over his diminished core, feeding enough magic into him to ignite a spark deep within him. Grillby’s head burst into a deep, orange blaze, flames bleeding through his clothes.

Grillby could have easily burned through the ropes binding his arms together, but as a monster of his words, he let them be. He sprang forth, pushing Chillby’s outstretched arm aside, and stopped when his head was inches away from Sans. Although his colder counterpart had been caught off guard by his sudden movement, Chillby did not pull the skeleton away. Instead, the purple elemental finally released Sans’s arms and shifted the two of them until he offered Sans to Grillby with his femurs spread apart. His other self smirked in challenge.

“Sans… will you... allow me to do this?” Grillby whispered, brushing his flames against the side of the other’s face. 

Sans immediately leaned into the warm sensation, and panted, “yes, grillbz, please!”

Those words were all he needed to hear for the jealousy and lust he’d been holding back to consume him. As Grillby brought out his tongue and licked up Sans’s sternum, forcing out lewd moans from the skeleton, he only had one goal in mind.

To give the monster that he’d loved — and had refused to admit for so long — the best time he could have and to make him come. Preferably as many times as possible. 

\-----

Sans was ashamed to admit how much both these versions of Grillby were turning him on, especially this universe’s one. It was one thing to accept and get sexually aroused by his best friend’s warm touches, but it was a whole different matter if it’s his meaner, worldly counterpart doing it. It didn’t help, with his sight gone, that he couldn’t even discern the flames dancing across his bones from Grillby’s own fire. 

It was fine, he had thought to himself when Chillby first began fondling his bones. He figured if Grillby wasn’t going to reciprocate his feelings, he’d settle for the next best thing — this other, purple version of Grillby. 

Stars, had he seriously fallen this low?

But as Sans felt the scalding heat stroke up his sternum, his mind went into bliss. He soon realized that Grillby’s flames were, by several ten degrees, warmer than the ones that had been caressing his bones. Sans arched his spine. The sharp pain from the burn left a tingling numbness that aroused him further. The noises spilling forth from his mouth, which he’d given up on holding back, increased in volume and intensity.

Sans felt Grillby slowly trail towards his pelvis, making his soul quiver in anticipation. Sans moaned and jerked his hips towards the stimulation, liquid magic trickling down the inner parts of his femurs. Without warning, a sizzling tongue plunged deeply into the bottom crevice of his soul, filling his entire being in a mix of blistering pain and pleasure. Sans screamed.

“ahh~! grillby! hah... hnngh!”

Sans ground his hips into the ministrations and jolted when cooler flames unexpectedly grazed down his neck. As Grillby’s tongue prodded and twisted around the heart-shaped organ, he felt pressure build up in his soul. Sans was overwhelmed with cool, almost cold, stings in between his vertebrae and the scorching, rough movements of Grillby’s appendage. 

All of Grillby’s feelings — his love, lust and envy from what Chillby had done — filled Sans. 

And he accepted them all. 

An expert flick at the top tip of his soul had Sans coming with a loud cry. Even through the dark tie wrapped around his head, Sans caught sight of the bright cyan from his orgasm. Crackling reached his nonexistent ears as he felt Grillby’s tongue lick up the fluid, racking his diminutive frame with violent shudders from the overstimulation. 

And the orange elemental didn’t stop there. Grillby must’ve had tons of experience with soul sex, since it didn’t take long for the familiar coil to tighten within Sans’s core once again. A clothed erection soon pushed against the back of his pelvis. 

Grillby’s sweltering heat moved away from him, leaving him strangely dissatisfied. 

“n-no! d-don’t… hah... stop! keep going…please!” Sans scrambled for Grillby.

He needed more. He needed to be filled until he burst.

“Hold your legs,” Chillby ordered.

Panting irregularly, and willing to do anything to continue, Sans grabbed his femurs in each hand as he was lifted up. Both fire monsters shifted against him, the shuffling of fabric and clinking of belts echoing within his mind.

“Grillby, you seem like a reasonable monster, since you are me. I propose we share this opportunity.”

“Sans is... not yours!” 

“Oh come on now. As they say, two is better. Imagine how good it’ll feel!”

A cool shaft rubbed against the bottom of Sans’s pelvis, and he gasped. The thought of having both Grillbys’ cocks pounding into him, fucking his soul, sent a pulse of arousal straight to his core, and his soul throbbed in anticipation.

“it would really… set my bones on fire, heh,” Sans uttered without thinking.

There was no movement or sound for an extended length of time, during which Sans cursed himself in embarrassment. 

“It seems Sans is quite willing. How cruel it would be to keep him hanging.”

All Sans heard was rustling and loud hissing before two thick shafts breached his pubic arch and pierced into his soul —one as hot as the lava in Hotland and the other as cold as the ice in Snowdin. Sans cried out. The searing heat and freezing chill had tears springing to his eye sockets. His arms shook as he tried to maintain a hold on his spread legs.

The harsh thrusting of the two fire monsters rocked Sans back and forth between Grillby and his counterpart, sparks of white hot pleasure ripping through him. Sans’s peak approached for the second time that evening, faster than before due to the two contrasting temperatures and rough treatment. Sans came hard when the two lengths were halfway up his ribs, but the elementals Continued their relentless assault. Losing their strength, Sans’s hands let go of his femurs and his limbs flopped down to his side.

A set of cool arms raised his pelvis up so both of their cocks hit the center of his soul. Sans keened, tears soaking through the tie. 

“ahhh… fuck!”

Embers caressed his face, it's hotness, heh, burning off the fabric covering his eye sockets. Only orange and purple filled his vision. Grillby and Chillby had lost their humanoid forms, their aroused magic smothering Sans within their flames. He squirmed and screamed helplessly at their rapid movements. Lava danced within his opened jaw, flooding his mouth, and traveling through his ribs. Simultaneously, ice poured through his eye sockets and wrapped around his limbs and spine. Both monsters’ passion evaded his soul and pushed everything else out. 

When Sans’s third orgasm tore through him, stars lined his vision. He didn’t know how much longer those two could last, considering they had yet to come, but he was exhausted beyond belief. He felt like he’d just run throughout the whole Underground without breaks.

“gah! too... much,” barely made it out of his mouth.

His words went unheard as the two elementals didn’t stop. Fire invaded every part of his being — around his bones, in between them, through every orifice that he possessed. When two pulsing souls sandwiched his own, his pubic arch stretched beyond its limit, Sans thought he would die from the overwhelming pleasure. One final thrust from both monsters later, and all three came together. 

Then, everything went black.

Sans woke up on something soft. He felt a tingling over his entire body, a sensation similar to the few times he’d burned his tongue. His eyes caught the sight of orange, and Grillby suddenly appeared in front of him. Concern and guilt marred his features.

“Sans…” the elemental’s flames flickered and shrank. “...I’m so sorry… I…”

Sans didn’t understand why Grillby was apologizing, unless it’s for one of the best nights he’s ever had.

“what’s got your matches in a box grillbz? you did nothin’ wrong.”

Grillby crackled loudly, turning away in shame.

“I thought… I was too rough… you had passed out… I could have,” the monster shuddered. “hurt you… and all this happened… because of me. and the way i spoke as if… i owned you...” Grillby dimmed.

Sans forced himself to sit up despite his aching body protesting the movement, and settled a hand on Grillby’s shoulder. The monster startled.

“don’t you go blamin’ yourself for something i wanted. i've, um, liked you for a while now. you could say… i’ve been enticed by your light, heh. and, uh, it’s nice to finally get a confirmation. ‘sides, i, uh, really enjoyed it. wouldntmindoinitagain,” Sans mumbled the last part, blushing furiously.

“... what?”

He sighed and restated, “i wouldn’t mind doin’ it again… if you’re willing.” He paused for a second, and then added, “just the two of us next time.”

Grillby’s face grew in size and flared yellow. Sans took that as a good sign. And sure enough, a pair of warm arms wrapped tenderly around him like a blanket. Before long, Sans found himself drifting back to sleep, this time in the arms of the monster he loved.

\-----

Chillby chuckled as he shut the door to his guest bedroom and went back downstairs. As much as he had a good time, he hated sharing, even with himself. Besides, he preferred to fuck his Sans all night with no breaks. Who would’ve thought the lazy skeleton had more stamina than this blue Sans. He only hoped his lover wouldn’t be upset with him fucking another version of him (and himself).

As Chillby neared his kitchen, he heard grunts and moans of arousal. Curious, he slammed opened the door, wondering who in the hell would dare to get off in his cooking area.

There, in the corner of the room, was Punk Hamster with a paw buried deep within his pants. His eyes were shut tightly, jerking his hips upward.

“Punk! What the fuck do you think you’re doing?!” Chillby snarled.

The rodent came with a scream. He took several deep breaths, and froze when his eyes fell upon Chillby’s glare.

“Boss! Sorry for getting off. That was just… hotter than anything I’ve ever seen.” Punk Hamster dug into his pocket and pulled out a handful of gold. “I’ll give ya half of my earnings of you let me watch again, or next time!”


End file.
